In automated tape libraries there exist cartridge storage slots or cells for holding tape cartridges for retrieval by a cartridge accessor. One of the important customer requirements for tape libraries is to have a very high density of tape cartridges per unit floor area. A method of increasing cartridge density within the library is to include storage slots that are deep enough to hold multiple cartridges. Particularly, for smaller tape libraries, deep slots can be advantageous when geometry constraints limit the possible locations of tape cartridges within a small area. When deep storage slots are utilized, it is desired to have a method of pushing the cartridge to the front opening of a slot in order for the cartridge accessor to grab the cartridge.
One known method for moving tape cartridges to the front of a deep storage slot uses a robotic mechanism to push the cartridges from the back of the slots to the front of the slots. This robotic mechanism can add significant cost to a library, as well as require significant space, negatively affecting available storage density within the library. Another known method for moving tape cartridges to the front of a deep storage slot uses a compression spring to push cartridges forward. One drawback to this method is that the spring itself must be relatively long in order to push the complete length of one or more cartridges. This causes the stack height of the spring to be quite significant, and causes the overall storage density within the library to be negatively affected. Another problem with the long spring is that it is subject to buckling under its compression load. Still another drawback is that the push force presented by the spring increases as the spring is loaded. This variation in spring force (dependant on the number of cartridges in the storage slot) requires that the force necessary to retain the cartridge from falling out of the slot also be variable. This is difficult and costly to accomplish. A method for pushing the cartridges forward that does not sacrifice storage density and works reliably and cost effectively is desirable.